Haemolysis

Haemolysis

This can be diagnosed by the use of a full blood count, and determining whether there is a presence of:

• Low haemoglobin count
• Low RBC count
• Low MCV (average volume of a single red blood cell)
• Increased reticulocyte count 

Within a haemolytic full blood count, the following traits can be observed:

• Polychromasia: this is the presence of an abnormally high number of red blood cells, whom have been released prematurely from the bone marrow. This is a sign of stress being applied to the bone marrow. These RBCs will have a slight gray/bluish hue to them. 
• Spherocytes: there are RBCs whom are sphere in shape, they have a smaller surface area for oxygen/carbon dioxide transport however they still have enough in order to maintain a healthy transport. The main different is their osmotic potential, they are more likely to carry out haemolysis in water than normal, biconcave disc shaped RBCs.
• Red cell fragments: these would be present in haemolytic anaemia as a result of burst RBCs. 

A direct antiglobulin test can carried out, however it is not 100% specific or sensitive to haemolytic anaemia. 

Urinary haemosiderin

Haemosiderin is an iron storage complex, however unlike ferritin, it is always found within the cells as apposed to circulating in the blood. It's molecular structure is poorly defined, however it appears to be a complex of denatured ferritin and other material. The iron within haemosiderin is poorly accessible when it is required. 

We look for urinary haemosiderin as this indicates the presence of haemoglobin in the glomerular filtrate. This is useful in proposing chronic intravascular haemolysis as haemosiderin may be present in the urine, even if no haemoglobin is detectable. IT will be detectable for many weeks after the incidence of haemolysis, but it will not be present at the initial onset of haemolysis, as the iron in the haemoglobin has to first be metabolised. 

Stains in order to detect urinary haemosiderin at applied parallel with a bone marrow slide, acting as a positive control, from a patient who has previously been found to have adequate iron stores. The Prussian blue stain can be used to visually identify haemosiderin, staining it a dark blue colour. 

If the staining causes an ambiguous result to form, this should always be consulted with a senior haematologist.  

If a sample is thought to be contaminated, it should not be used in diagnosis.

Biochemical tests

Testing for bilirubin is useful as this indicates the break down of haemoglobin as it is a product of such an event. 

Testing for haptoglobin is useful as this tends to bind to free haemoglobin in the blood, thus there will be less free haptoglobin in the blood. 

Testing for lactate dehydrogenase (LDH) in the blood is useful as this is increased when haemolytic anaemia is present, this is because LDH can be found within RBC, and is consequently released as a result of their haemolysis.